Effects of animal gender and age, use of a growth stimulant, and supplementation with grain alone or grain plus other substances on ADG by growing beef cattle grazing bermudagrass paddocks with sod-seeded rye, wheat, and ryegrass were determined. Two grazing experiments (Exp. 1: late winter through mid-spring; Exp. 2: late spring through mid-summer) were conducted. Experiment 1 used 96, 12- to 13-mo-old Simmental-cross calves (heifers, 240 kg; steers, 272 kg), half of which were implanted with zeranol. Within each implant treatment, cattle received no supplement or .5% BW (DM) of ground corn alone or plus a mix of protein meals, zinc sulfate, thiamin-HCl, or salt. Daily gain was higher (P less than .05) with than without supplementation and was similar (P greater than .10) among supplement treatments. In Exp. 2, 96 crossbred beef steers, approximately 7 (230 kg) or 15 mo old (250 kg), were not supplemented (control) or received .5% BW (DM) of ground corn on d 1 to 84 (C-C), corn plus a protein meal mix on d 1 to 84 (CP-CP), corn on d 43 to 84 (O-C), corn plus the protein meal mix on d 43 to 84 (O-CP), or corn on d 1 to 42 and corn plus the protein meal mix on d 43 to 84 (C-CP). Daily gain on d 1 to 84 was affected (P less than .05) by supplement, age, implant, and the supplement x implant interaction (nonimplanted: .37, .56, .68, .40, .49, and .49; implanted: .37, .62, .54, .49, .70, and .71 kg for control, C-C, CP-CP, O-C, O-CP, and C-CP, respectively).

Three experiments were conducted with cattle consuming bermudagrass hay to determine whether low-level supplements of whey alone, corn alone, or whey plus corn affect feed intake, digestion, and(or) BW gain. Six ruminally and duodenally cannulated beef cows (574 kg), used in a Latin-square trial (Exp. 1), were fed bermudagrass hay without supplementation (control) or with 2.8% whey (low whey, LW), 5.6% whey (high whey, HW), 17.4% ground corn (C), 2.8% whey plus 14.9% corn (C-LW), or 5.6% whey plus 12.4% corn (C-HW). Supplementing with whey and(or) corn increased ruminal butyrate (8.8, 9.4, 10.0, 9.6, 10.5, and 11.0 mol/100 mol of total VFA for control, LW, HW, C, C-LW, and C-HW, respectively; SE = .20). Supplements did not affect microbial N flow at the duodenum. Six Holstein steer calves (158 kg) in a Latin square (Exp. 2) consumed bermudagrass hay ad libitum alone (control) or with .075 or .15% BW whey (LW and HW, respectively), .5% BW ground corn (C), or corn-whey mixes made by substituting whey for corn (C-LW and C-HW). Substituting .15% BW of whey for corn increased (P less than .05) total OM intake slightly (3.99, 3.84, 3.75, 4.11, 4.28, and 4.47 kg for control, LW, HW, C, C-LW, and C-HW, respectively; SE = .10). In an 84-d randomized block experiment (Exp. 3), 96 beef calves (194 kg) consumed (ad libitum) low-quality bermudagrass hay alone or with C, LW, HW, C-LW, or C-HW supplements.(ABSTRACT TRUNCATED AT 250 WORDS)

Two experiments were made to determine the effects on digestion characteristics and live-weight (LW) gain of cattle consuming bermudagrass of supplementing with ground maize, soya-bean meal or a maizegluten-blood meal mix alone or maize plus the protein supplements. Experiment 1 was a Latin-square design with 14-day periods using six beef cows fitted with rumen and duodenal cannulas (490 kg). Cows were given bermudagrass hay at 12-7 g/kg LW alone (control, C) or with 2-4 g/kg LW of ground maize (M), 0-98 g/kg LW of soya-bean meal (S), 0-53 g/kg LW of maize-gluten plus 0-17 g/kg (dry matter basis) of blood meal (GB), M plus S (M + S) or M plus GB (M + GB). Nitrogen (N) intake was 106, 123, 143, 148, 166 and 166 g/day; total N at the duodenum was 101, 124, 117, 126, 140 and 161 (s.e. 5-91) g/day; and post-ruminal N disappearance was 61, 77, 72, 84, 87 and 110 (s.e. 5-6) g/day for C, M, S, GB, M + S and M + GB, respectively. In experiment 2, 96 crossbred beef heifers (203 kg LW) implanted with 200 mg testosterone and 20 mg oestradiol benzoate were allotted to 12 groups by LW (two groups per treatment). Heifers grazed bermudagrass paddocks for 84 days in two 42-day periods and supplement treatments were those in experiment 1. A period x treatment interaction in LW gain was noted (P < 0-05). LW gain was 0-78, 0-81, 0-79, 0-76, 0-70 and 0-95 kg in period 1 and 0-46, 0-51, 0-56, 0-53, 0-64 and 0-61 kg in period 2 for C, M, S, GB, M + S and M + GB, respectively (s.e. 0-049). In conclusion, duodenal flow and post-ruminal disappearance of N were similar for the protein sources when offered singularly, but when given with maize values were greater for the mix of protein meals high in ruminal undegradable protein as compared with soya-bean meal. LW gain by heifer calves grazing bermudagrass was increased only by supplementation with ground maize plus the protein meal mix of low ruminal degradability.

Growing cattle were supplemented with substances to lessen or increase ruminal ammonia level to determine if consumption of moderate- to high-crude protein (CP) forage is limited by high ruminal ammonia absorption. In Experiment 1 (5 x 5 Latin square), five Holstein steers (198 kg) had ad libitum access to alfalfa cubes (17% CP) without supplementation or with corn at 0.25 or 0.75% body weight (BW) alone (LC or HC) or with 0.06% BW of zeolite (chabazite; LC-Z and HC-Z). Total daily organic water (OM) intake was not affected by treatment (6.08, 6.14, 6.11, 6.19 and 6.09 kg for control, LC, LC-Z, HC and HC-Z, respectively; SE 0.25). In Experiment 2, Simmental crossbred beef calves grazed fescue-clover paddocks in the spring (clipped forage: 21 to 27% CP) for 84 days and were supplemented with 0.25 or 0.75% BW corn alone or with added zeolite (0.06% BW) or lasalocid (0.5 mg/kg BW). Daily gain did not differ among treatments (1.24 to 1.31 kg/day). In Experiment 3 (6 x 6 Latin square), six Holstein steer calves (168 kg) had ad libitum access to medium-quality, orchardgrass-clover hay (15% CP). Steers received one of the following six treatments: no supplement (Control), 0.35% BW ground corn (C), corn plus 0.049% BW urea (C-U), 0.35% BW soybean meal (S), 0.205% BW feather meal (F) or 0.103% BW feather meal, 0.052% BW blood meal and 0.067% BW corn gluten meal (F-BG). Total daily OM intake was 5.00, 5.14, 5.00, 5.11, 4.84 and 4.70 kg for control, C, C-U, S, F and F-BG, respectively (SE 0.13). In Experiment 4 (6 x 6 Latin square), six Holstein steer calves (226 kg) were fed 0.75% BW of alfalfa cubes (19% CP) plus ad libitum access to medium- to high-quality orchardgrass hay (16% CP). Steers received one of the following six treatments: no supplement (Control), corn at 0.25% BW alone (c) or mixed with 0.12% BW peanut skins (C-PSK), a mix of high-CP feedstuffs high in ruminal escape protein (0.029% BW blood meal, 0.038% BW corn gluten meal and 0.028% BW feather meal; C-REP), 0.139% soybean meal (C-S) or soybean meal plus peanut skins (C-PSK-S). Total daily OM intake was 6.16, 6.25, 6.13, 6.52, 6.50 and 6.60 kg for control, C, C-PSK, C-REP, C-S and C-PSK-S, respectively (SE 0.10).(ABSTRACT TRUNCATED AT 400 WORDS)

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